In general, a light-sensitive material has silver halide emulsion layers which are sensitive to the three original colors of red, green and blue. A color image is reproduced by the subtractive method in which the three color formers (couplers) contained in the respective emulsion layers are subjected to development into a color having a complementary color to the color to which each of the layers is sensitive. This color image obtained by photographically processing the light-sensitive material generally consists of an azomethine dye or indoaniline dye formed by the reaction of the oxidation product of an aromatic primary amine developing agent with a coupler.
However, such a light-sensitive material is still insufficient to meet the demand for a high quality material. Significantly, a developed dye obtained from a yellow dye-forming coupler still has several problems which have to be overcome. Firstly, the absorption coefficient of the developed dye is small compared with those of dyes obtained from a magenta dye-forming coupler and a cyan dye-forming coupler, and this necessitates the use of more yellow coupler in order to obtain the same density as magenta and cyan coupler-based materials. Secondly, the hue thereof is not necessarily sufficient for accurately reproducing an original color. Thirdly, the developed dye and unreacted coupler are not stable in light, humidity and heat, and exposure to sunlight over a long period of time and storage at high temperature and humidity cause the dye image to fade and discolor and cause the background to color. These problems cause deterioration of the image quality.
In order to solve these problems, it has been proposed to improve the couplers and include additives, for example, a specific phenol series compound and a sulfonamide series compound. However, these proposals do not sufficiently solve the problems.
Meanwhile, it is known to use an anti-fading agent and a UV absorber for the couplers. Known anti-fading agents include, for example, hindered piperidines, hindered phenols, amides, hydrazines, bisphenols, a phosphrous compound, and a thiane compound.
However, while these compounds improve the fastness of an image, the improvement is insufficient. In addition, they are scarcely effective in improving the color developing characteristics or in increasing the absorption coefficient of the dye.
The improvement in performance by using additives (for example, the above anti-fading agent and UV absorber) is limited. This has resulted in increasing attempts to improve performance by modifying the structural design of the coupler itself.
Proposals to improve the fastness of an image by using couplers having specific groups are disclosed in JP-A-1-180547 (the term "JP-A" as used herein means an unexamined Japanese patent application), JP-A-1-191141, U.S. Pat. Nos. 4,824,771 and 4,758,501. However, while the fastness of the image has been improved, it is unsatisfactory, since hue is changed, fog is generated and dispersion is inferior.
Further, yellow couplers having phosphoric acid or phosphonic ester and amide groups are proposed in U.S. Pat. No. 4,026,709. However, while they have excellent solubility, they provide an image having insufficient fastness, and hue or color developability have not yet reached a satisfactory level. The couplers described in U.S. Pat. Nos. 5,194,369 and 5,118,599, European Patent Publications 447969 and 482552, and JP-A-4-184434 have insufficient light fastness and also have a problem in that color developability is lowered due to the change in development processing composition.